Synergistic antioxidants and their use



ilnited, rates Patent SYNERGISTIC ANTEGXEANTS AND THEIR USE Eugene F.Hill, Birmingham, Mich, assignor to Ethyl Corporation, New York, N. Y, acorporation of Delaware No Drawing. Application January 26, 1953, SerialNo. 333,371

Claims. (ill. 44-69) The present invention relates to the protection ofmaterials that are subject to deterioration by contact with oxygen inany of its forms.

Certain hydrocarbon-type materials in wide use are subject todeterioration, sometimes fairly rapidly, when exposed to air andparticularly where the air might have some ozone content. By way ofexample, gasolines and diesel engine fuels now enjoying wide-spread useare for practical reasons manufactured with a relatively high content ofolefinic-type hydrocarbons. These materials, upon standing, will reactwith oxygen and will at least be partially converted to a form that isnot desirable. Thus, olefinic gasolines will show a strong tendency todeposit gums which will interfere with the filtering of the gasoline byclogging up the filters and even cause fuel-passing valves to stick. Inaddition, gummy deposits often foul spark plugs and thereby causemisoperation of the engine. These same general type of dilficulties areexperienced with diesel fuels.

In the past it has been found desirable to add antioxidants to the abovetypes of oxygen-sensitive materials. However, with the progress of time,fuels have come to contain more and more olefins and engines have becomemore efficient and powerful so that the engine and fuel specificationsare more rigid. The continuous use of prior art antioxidants accordinglyresults in the build-up of the antioxidant concentration to the pointwhere it cannot be tolerated by some engines.

Among the objects of the present invention is the provision of novelantioxidant compositions that are more efiective than the prior artantioxidants.

Additional objects of the invention include the pro vision of mixturesof olefin-type hydrocarbons with a synergistic antioxidant compositionthat makes possible more effective protection of the hydrocarbons.

The above as well as still further objects of the present invention willbe more clearly understood from the following description of several ofits exemplifications.

It has been discovered that standard antioxidants selected from theclass consisting of phenylenediamines, aminophenols and trialkylphenols,when mixed with a compound of the class consisting of ascorbic acid andits esters, show an unexpectedly high antioxidant etfect in protectingolefin-type hydrocarbons that are subject to deterioration by oxygen.This effect is particularly significant inasmuch as ascorbic acid andits esters show very little or no antioxidant value in connection withthese materials when used as a primary antioxidant. The

synergistic etfect appears to extend to antioxidant compositions havingfrom to 80 percent of ascorbic acid or its ester, the balance beingessentially one or more of the above-named standard antioxidants. Bestresults are obtained, however, with an antioxidant composition havingabout twice as much of the standard antioxidant as ascorbic acid or itsesters.

The following examples are typical of the improvements resulting fromthe present invention. In these examples the deterioration tendency hasbeen measured by Pa nted Meta 91 5 2 determining the induction periodvarious samples of materials require before beginning to react withoxygen under accelerated reaction conditions. The specific method usedis a standard one adopted by the American Society of Testing Materialsfor determination of the oxidation stability of gasoline (inductionperiod method), ASTM designation: D525-46, and is fully described inPart III-A, ASTM Standards for 1946. According to this method, theinduction period is the period during which there is no absorption ofoxygen by the test material as indicated by a time delay before thepressure drops in a testing bomb containing the test material at C. withoxygen at an initial pressure of 100 pounds per square inch gauge. Allpercentages are by weight.

Hydrocarbon Induction Material Tested Protecting Addition Period inMinutes G1 Gasoline- None 118 Do 0.0075% N .N-di-secbutyLp-phenylenedi-394 amine A. 0.005% A +0.0025% ascorbic acid 533 N 90 260 315 A 3400.005% A +0.0025% ascorbic acid 400 0.0025% A +0.00125% ascorbylpalrnitate 350 0.005% A +0.0025% ascorbyl palmitate 430 None 0.003725% A310 0.0025% A +0.00125% ascorbyl palmitate. 355 0.0075 0 l v 400 0.005%A +0.0025%ascorbyl palmitate 490 In the above examples the G1, G2, andG3 gasolines are standard commercially available automotive gasolineswhich, when untreated, are normally susceptible to deterioration in thepresence of oxygen. The characteristics of the above gasolines are asfollows:

Distillation Range,

(29.5 in. Hg) (29.2 in. Hg)

Olefins; 18.4% Aromatics" 23. 6% Paraflins... 36. 5%

0100115 26.7% Aromatics" 18.1% Paraffins. 41.7%

Hydrocarbon-Type.

It should be noted that the ascorbic acid shown above to have asynergistic antioxidant eifect when combined with theN,N'-di-sec-butyl-p-phenylenediamine has when used by itself anantioxidant behavior which is very small, being about one-tenth that ofthe N,N'-di-secbutyl-p-phenylenediamine. The ascorbyl palmitate of theseexamples has, when used alone, no appreciable antioxidant effect.

Although the above examples show the value of the present invention inconnection with stock gasolines, the same general improvements areobtainable with other olefin-type materials such as diesel fuels thattend to deteriorate in the presence of oxygen. The effect with gasolinesis obtained whether or not the gasoline is leaded, that is containsadded tetraethyllead along with its usual lead scavenger complement, asfor example ethylene dibromide or ethylene dichloride.

When other of the above mentioned prior art standard antioxidants aresubstituted for the N,N'-di-sec-butyl-pphenylenediamine equally goodsynergistic improvement is obtained. Specific classes of suitable priorart antioxidants showing the synergism when admixed or otherwise used inconjunction with ascorbic acid and esters thereof are phenylenediamines,aminophenols and trialkylphenols. Illustrative examples of thephenylenediamines include such materials as unsubstitutedp-phenylenediamine, unsubstituted o-phe'nylenediamine, as well asderivatives of these materials in which either or both amine groups arealkylated such as N,N-dimethyl-p-phenylenediamine,ethyl-p-phenylenediamine, N-methyl-N' n propyl pphenylenediamine,stearyl-p-phenylenediamine, N-methyl- N'-lauryl-p-phenylenediamine,N,N'-diethyl-o-phenylenediamine, N-methyl-o-phenylenediamine,N-butyl-N'-iso- 'propyl-o-phenylenediamine, N-stearyl ophenylenediamine, N-methyl-N'-lauryl-o-phenylenediamine,Z-aminodiphenylamine, 4-aminodiphenylamine, and the like. 11-

lustrative examples of aminophenols which can be ernor they are alldifierent, and the groups range from methyl to decyl.

Instead of the ascorbic acid or ascorbyl palmitate other ascorbic acidesters can be used to give the equivalent results. Such other estersinclude such substances as ascorbyl formate, ascorbyl acetate, ascorbyllactate,

ascorbyl succinate, ascorbyl maleate, ascorbyl propionate,

ascorbyl picrate, ascorbyl benzoate, ascorbyl salicylate,

ascorbyl monomalonate, ascorbyl dimalonate, and the like.

In all the above modifications, the same general formulation ofingredient proportion is effected. The concentration of antioxidantcomposition in the material being protected can be varied from about0.01 percent down to the smallest concentration that will be elfective.Concentrations larger than 0.01 can be used but are not desirable.

As many apparently widely different embodiments of the invention may bemade Without departing from the spirit and scope hereof, it isunderstood that the invention is not limited to the specific embodimentshereof except as defined in the appended claims.

What is claimed is:

l. Gasoline normally tending to deterioriate in the presence of oxygen,and containing a mixture of an N,N' -dialkyl phenylene diarnineantioxidant and a synergist selected from the class of ascorbic acid andascorbyl palmitate, said synergist being present in an amount of from 10to 80 percent of the total amount of the mixture, the total mixturebeing present in an amount suificient to stabilize the gasoline.

2. The combination of claim 1 in which the N,N'-diallryl phenylenediamine is N,N'-di-s ec-butyl-p-phenylene diamine.

3. Thecombination of claim 2 in which the synergist is ascorbic acid.

4. The combination of claim 2 in which the synergist isascorbyl'palmitate. l 7

5. A leaded olefinic gasoline containing about 0.005

' to about 0.01 percent by weight of a mixture of two parts ofN,N'-di-sec-butyl-p-phenylenediamine with one part of a synergistselected from the class of ascorbic acid and ascorbyl palmitate.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Industrial and Engineering Chemistry, July 1926, page 691.

Riemenschneider:

Oil and Soap October 1944, pp. 307-309. I

5. A LEADED OLEFINIC GASOLINE CONTAINING ABOUT 0.005 TO ABOUT 0.01PERCENT BY WEIGHT OF A MIXTURE OF TWO PARTS OFN,N''-DI-SEC-BUTYL-P-PHENYLENEDIAMINE WITH ONE PART OF A SYNERGISTSELECTED FROM THE CLASS OF ASCORBIC ACID AND ASCORYBL PALMITATE.